Fixes in 1990/jaw

The example commands in the judges' comments had some problems that gave
an error message when running them.

I have also figured out the apparent problem with macOS in the command
under the try section being:

    echo "Quartz glyph jocks vend, fix, BMW." | compress | ./btoa | ./jaw

But it's not actually a problem. It uses perror() and under macOS with
errno == 0 it shows:

    Undefined error: 0

whereas linux shows 'Success'. So it's not actually a problem with the
entry at all. In fact the condition that triggers that call is the same
in both linux and macOS.

I've updated bugs.md to note this and I also updated the README.md to
note it (and to refer to the bugs.md file for more details).

The thank you to me is because I missed it earlier on when I fixed the
scripts, simple though the fixes were.

1990/jaw/.gitignore

@@ -1,3 +1,6 @@
 atob
 jaw
 zcat
+receive
+unshark
+unshark.c